The present invention relates to a technology of how to perform defect registration of a data sector located on a magnetic disk, and more particularly to a technology for correctly registering, in a simple way, a data sector that is potentially defective.
As for the magnetic disk that is a recording medium of a magnetic disk drive, a plurality of data tracks (hereinafter merely referred to as “track”) are concentrically defined on each recording surface by servo data, and a plurality of data sectors (hereinafter merely referred to as “sector” unless it is particularly necessary otherwise) are defined in each track in the circumferential direction. A sector is a smallest unit of writing data to the magnetic disk, and is defined, for example, as a storage block having a length of 512 bytes. In a manufacturing process of the magnetic disk drive, a bad sector which has been detected by carrying out a read/write test for all sectors is judged to be a defect sector, and its address is then registered in a primary defect map (hereinafter referred to as “PDM”) to disallow the use of the defect sector. A sector in which a defect occurs after a user starts using the magnetic disk is registered in a reassign defect map (hereinafter referred to as “RDM”) so that an address of the defect sector is reassigned to an alternate sector which is prepared beforehand in a specified area of the magnetic disk.
A patent document 1 (Japanese Patent Laid-Open No. 2001-23310) discloses the configuration of PDM in which consecutive defect sectors are registered. A patent document 2 (Japanese Patent Laid-Open No. Hei 7-334933) discloses the technology for judging whether or not a scar occurs in the radial direction on a disk. A patent document 3 (Japanese Patent Laid-Open No. 2001-351201) discloses the technology for detecting a random defect and a vertically oriented defect with few errors without inspecting all tracks.